My son, Jonah, came home from preschool one afternoon in a fidgety mood, wiggling his fingers wildly and whispering to himself. I was trying to figure out why he was so restless (Too much sleep? Too little time on the playground?) when he proudly announced that he was practicing a new skill he was learning at school: sign language.

It's not news that signing with babies can help them communicate before they can talk, but it's a more recent trend to use sign language with older kids. Experts say that teaching children this age the signs for words and the alphabet can help with letter recognition and build their vocabulary. Kids just think it's fun.

Giving sign language a try at home shouldn't be too tricky. "Three- and 4-year-olds usually find signing easy and entertaining because it taps into their natural tendency to communicate using their body," explains Jan Christian Hafer, Ed.D., director of general studies at Washington, D.C.'s Gallaudet University, which focuses on serving deaf students. And there are plenty of easy-to-use resources available. Libraries often stock books and DVDs geared toward signing with kids -- and websites, such as lifeprint.com, allow you to see sign language in action. Check out how your kid can benefit from this hands-on language.

Why it Helps: It Increases Kids' Vocabulary

Studies of preschoolers in Maryland found that those who were introduced to American Sign Language (ASL) words, such as signs for the weather, colors, numbers, and feelings, did better on vocabulary tests than their peers who weren't taught to sign. One reason? ASL words are often iconic, meaning they tend to look like what they represent, says study author Marilyn Daniels, Ph.D., professor emerita in the Department of Communication at Penn State University and author of Dancing With Words. This similarity helps kids grasp the meanings and remember new words introduced through signing. When beginning to sign with your child, choose signs that evoke a mental image of the word you are trying to teach. For example, the word listen involves cupping your hand behind your ear. Then introduce new words she doesn't already know the meanings of. While signing the word invent (put index finger on forehead, point it upward and then down in front of you), explain that the word means to take an idea that's in your head and turn it into something that is real and useful to the world.

More Ways Sign Language Helps

Why it Helps: It Teaches the ABCs and Spelling

Your preschooler is probably already learning to recognize and write his letters. Since many of the ASL hand symbols resemble the shape of letters in the written alphabet, learning his manual ABCs could give him a boost with this new skill set. And young children who learn how to turn their fingers into easy words like C-A-T and continue to practice finger spelling as they grow often have an edge when it comes to spelling. That's because during the elementary-school years, and perhaps even later, these kids can turn to their fingers to remind themselves how to spell a word. You can also teach your child to finger-spell his name and other simple words. At bathtime, use your hands to ask him to get in the T-U-B. As the sun goes down, point him in the direction of B-E-D.

Why it Helps: It Encourages Communication

Kids this age still may not have the vocab to get their point across, which is why your child may react to a playmate taking away her doll by hitting her friend instead of asking for it back. Having sign language to rely on gives kids another option for communicating their feelings. "We learn gestures before we learn words. When we're frustrated, we sometimes revert to those instincts," explains Wendy Crawford, principal of GrenlochTerrace Early Childhood Center, in Sewell, New Jersey.

Once your kid has mastered a few sign words, start incorporating feelings into the mix -- like proud, mad, and happy. If she does throw a tantrum, remind her how to sign the word mad (put palm in front of face and crunch fingers). Being able to express her frustration can often stop (or at least delay) a meltdown. Similarly, teach your child the sign for sorry (circular motion of hand around heart with sad face). Kids are usually quicker to use their hands to apologize than they are to swallow their pride and actually verbalize it. It's likely that the other child won't know sign language, and your kid will eventually have to speak the words, but by then emotions on both sides may have cooled a bit.